This invention relates in general to electro-hydraulic brake systems and in particular to an electrical interconnection between an electronic control unit and a hydraulic valve body for an electro-hydraulic brake system which uses wire form buttons.
An Electro-Hydraulic Brake (EHB) system combines the advantages of an electric braking system with components of a conventional hydraulic brake system. Thus, an EHB system can be considered as an intermediate hybrid system which includes features of both a conventional hydraulic brake system and a brake by wire system (BBW). By utilizing conventional hydraulic brake components, development and conformance costs and times are reduced.
Referring now to FIG. 1, there is shown, generally at 10, a typical EHB system. The EHB system 10 includes a pedal unit 11 which is hydraulically connected to a Hydraulic Control Valve (HCV) 12. The HCV 12 forms an interface between the pedal unit 11 and a pair of conventional hydraulically actuated vehicle front wheel brakes 13 and a pair of conventional hydraulically actuated vehicle rear wheel brakes 14.
The pedal unit 11 includes a tandem master cylinder 15 which is supplied with brake fluid from a master cylinder reservoir 16. The master cylinder 15 is connected by a conventional mechanical linkage to a vehicle brake pedal 17. The brake pedal 17 also is coupled to a displacement transducer 18 which generates an electrical signal having an amplitude which is proportional to brake pedal travel. One chamber of the master cylinder 15 is connected by a first hydraulic brake line 19 while the other chamber of the master cylinder 15 is connected to a second hydraulic brake line 20. The pedal unit 11 also includes a normally closed valve 21 which connects the first brake hydraulic brake line 20 circuit to a pedal travel simulator 22. The pedal travel simulator 22 is an electro-hydraulic device which is operative during operation of the EHB system 10 to provide brake pedal resistance and force as feedback to the vehicle operator.
The HCV 12 includes a first normally open isolation valve 23 which is connected between the first hydraulic brake line 19 and one of the front wheel brakes 13 and a second normally open isolation valve 24 which is connected between the second hydraulic brake line 20 and the other of the front wheel brakes 13. Each of the front wheel brakes 13 is connected through an isolator piston 25 to a pair of proportional control valves 26 whose purpose will be explained below. The second valve of each pair of proportional control valves 26 is connected to a corresponding rear wheel brake 14. The isolator pistons 25 hydraulically isolate the front wheel brakes 13 from the rear wheel brakes 14. As shown in FIG. 1, the front wheel brakes 13 are hydraulically connected through a first balance valve 27. Similarly, the rear wheel brakes 14 are hydraulically connected through a second balance valve 28.
The HCV 12 further includes a motor driven pump 35 as a source of pressurized brake fluid for actuation of the wheel brakes 13 and 14. The pump 35 has an intake port which draws brake fluid through a hydraulic line 36 from the master cylinder reservoir 16. The pump 35 also has a discharge port which is connected through each of the proportional control valves 26 to a corresponding front or rear wheel brake 13 or 14. Each of the proportional control valves 26 includes a discharge port which is connected though a hydraulic discharge line 38 to the master cylinder reservoir 16. The discharge port of the pump 35 also is connected through a relief valve 39 to a high pressure accumulator 40.
A plurality of pressure sensors are included in the EHB 10. The pressure applied to the HCV 12 by the master cylinder 15 is monitored by a brake actuation pressure sensor 45 which is illustrated in FIG. 1 as being mounted in the first hydraulic brake line 19 between the master cylinder 15 and the first isolation valve 23. Alternately, the brake actuation pressure sensor 45 can be mounted in the second hydraulic brake line 20 between the master cylinder 15 and the second isolation valve 24 (not shown). The brake actuation pressure sensor 45 is rated to measure relatively low pressures which are on an order of magnitude of 60 bar (900 psi). A wheel brake pressure sensor 47 is included in each hydraulic line connecting each proportional control valve 26 to the associated wheel brake. The wheel brake pressure sensors 47 monitor the pressure being applied to the associated wheel brake and are rated to measure relatively high brake actuation pressures which are on an order of magnitude of 200 bar (3,000 psi). An accumulator pressure sensor 48 is connected to the high pressure accumulator 40 and monitors the output pressure of the accumulator 40. When the pump pressure exceeds the accumulator pressure or when the relief valve 39 is open, the accumulator pressure sensor 48 measures the pump output pressure. The accumulator pressure sensor 48 is also rated to measure relatively high pressures which are on an order of magnitude of 200 bar (3,000 psi).
The solenoid valves and pressure sensors are electrically connected to a microprocessor (not shown) which is included in an Electronic Control Module (ECU) (not shown). The ECU can either be mounted upon the HCV 12 or located remotely from the HCV 12. When the ECU is mounted upon the HCV 12, the combined unit is typically referred to as a Hydraulic Control Unit (HCU). The ECU microprocessor is programmed with appropriate software to monitor the output signals from the pressure sensors 45, 47 and 48 and the brake pedal transducer 18. The microprocessor is responsive to the sensed pressures and displacement of the brake pedal transducer 18 to energize the pump 35 and close the isolation valves 23 and 24. The microprocessor then selectively actuates the proportional control valves 26 to supply pressurized hydraulic fluid for actuation of the wheel brakes 13 and 14.
The operation to the EHB 10 will now be described. During vehicle operation, the microprocessor associated with the ECU continuously receives electrical signals from the brake pedal transducer 18 and the pressure sensors 45, 47 and 48. The microprocessor monitors the condition of the brake pedal transducer 18 and the pressure signals from the brake actuation pressure sensors 45 for potential brake applications. When the vehicle brake pedal 17 is depressed, the brake pedal displacement transducer 18 generates a displacement signal. Simultaneously, the brake actuation pressure sensor 45 generates a signal which is proportional to the force applied to the brake pedal 17. The microprocessor is operative to combine the displacement and force signals into a brake command signal. The microprocessor software is responsive to the brake command signal to actuate the pump motor and close the isolation valves 23 and 24 to separate the master cylinder 15 from the wheel brakes 13 and 14. The microprocessor then selectively operates the proportional control valves 26 in the HCV 12 unit to cyclically relieve and reapply hydraulic pressure to the wheel brakes 13 and 14. The hydraulic pressure applied to the wheel brakes 13 and 14 is adjusted by the operation of the proportional control valves 26 to produce adequate brake torque to decelerate the vehicle in accordance with the brake command signal generated by the vehicle operator.
If the EHB system 10 should fail, the isolation valves 23 and 24 return to their normally open positions to provide unassisted push though braking by allowing direct hydraulic communication between the master cylinder 15 and the front wheel brakes 13.
Referring again to the figures, a sectional view of a typical ECU 50 is illustrated in FIG. 2. The ECU 50 is mounted upon a HCV 12 to form a HCU 52. The ECU 50 includes a housing 54 which is typically injection molded from a plastic material. A metal cover 56 is attached to the upper edge of the housing 54 A main Printed Circuit Board (PCB) 58 is mounted upon the lower surface of the cover 56. Accordingly, the cover 56 functions as a heat sink for the main PCB 58. The EHB system control electronics 59 are mounted upon the main PCB 58. A male electrical connector 60 is mounted upon the lower surface of the main PCB 58 and extends in a downward direction in FIG. 2. Similarly, coil lead wires 62 extend from the main PCB 58 to a plurality of solenoid coils 64 (one shown) which are disposed within the housing 54. The male connector 60 and coil lead wires 62 are wave soldered to the main PCB 58 and the associated openings in the cover 56 are sealed with a potting material 66. A seal 67 is disposed between the lower edge of the housing 54 and the HCV 12. The ECU 50 is removeably attached to the HCV 12 by a plurality of threaded fasteners (not shown).
As described above, the HCV 12 carries a plurality of solenoid valves 68 (not shown). Each of the valves 68 has a sleeve 69 which extends upward in FIG. 2 from the upper surface of the HCV 12 and into an associated solenoid coil 64. The HCV 12 also carries a Pressure Sensor Cluster (PSC) 70 which is attached to the HCV 12 by a plurality of threaded fasteners 72. The PSC 70 includes a manifold 74 having a plurality of bores 75 formed therein (one shown). A cylindrical pressure sensing element 76 is disposed in each of the bores 75 formed in the PSC manifold 70. A transfer tube 78 extends from the HCV 12 and into each of the pressure sensing elements 76. The transfer tubes 78 communicate with interior passages formed in the HCV 12 to supply pressurized brake fluid to the pressure sensing elements 76. A pressure sensing array 79 is mounted upon the top surface of each pressure sensing element 76. The pressure sensing array 79 is connected by wire bonds 80 to a PSC PCB 82 which is mounted upon the top surface of the PSC 70. The PSC PCB 82 carries a signal conditioning circuit 84. A female electrical connector 86 also is mounted upon the PSC PCB 82 and cooperates with the male connector 60 mounted upon the main PCB 58 to provide an electrical interface between the pressure sensing elements 76 and the EHB control electronics 59. A more detailed description of the PSC 70 will be found in co-pending U.S. patent application Ser. No. 09/448,116, which is hereby incorporated by reference.
This invention relates to an electrical interconnection between an electronic control unit and a hydraulic valve body for an anti-lock brake system which uses wire form buttons.
As described above, it is known to connect the main PCB in an EHB system ECU to a PCB for a PSC with an pair of male and female electrical connectors. However, both the male and female connector are rigidly soldered to their respective PCB""s. Accordingly, significant horizontal and vertical stack up tolerances of the individual components can prevent proper mating of the connectors. Additionally, such mechanical connectors can be unreliable. Alternately, the PSC PCB can be wire bonded to the main ECU PCB; however, such wire bonding must occur during final assembly and requires that the ECU be sealed after the wire bonding. It is possible to provide terminals for the PSC PCB which extend through the main ECU PCB. The terminals are then soldered to the main ECU PCB at the final assembly plant. Again, such a process requires the addition of a soldering process at the final assembly plant which must take place on a large and bulky HCU. Finally, the PSC could be assembled into the ECU at the ECU assembly plant with the PSC terminals soldered to the main ECU PCB. The combined ECU and PSC would then be assembled to the HCV at final assembly. However, this approach requires that the threaded fasteners which secure the PSC to the HCV would extend through the ECU housing and require sealing after installation. Accordingly, it would be desirable to provide an improved electrical connector between the PSC and the main ECU PCB.
The present invention contemplates an electrical connector including at least one conductor having a first end adapted to be secured to a printed circuit board and a second end opposite from the first end. The connector also includes a member formed from an electrically insulative material, the member having a bore formed therethrough which has a first end and a second end opposite from the first end. The first end of the bore receives the second end of the conductor and a wire form button is disposed within the bore in contact with the second end of the conductor. The wire form button extends from the second end of said bore. The connector is formed as a spring which is operative to urge the block and wire form button in a direction away from the first end of said conductor.
It is further contemplated that the connector can include a plurality of conductors and wire form buttons. The connector also can include a second block of insulative material having a plurality of bores formed therethrough with the first end of each conductor extending through one of the bores.
The invention also contemplates an electrical connector assembly which includes the above connector. The assembly includes first and second printed circuit boards. The first end of the conductors are secured to the first printed circuit board. The second printed circuit board has plurality of contact pads formed thereon. Each of the contact pads corresponds to one of the conductors. The spring action of the connectors urges the wire form buttons into contact with the contact pads to electrically connect the first printed circuit board to the second printed circuit board.
The electrical connector assembly can be mounted within a housing which is removeably attached to a hydraulic control valve. The housing can be formed with a pair of integral support arms extending across the interior thereof. The support arms receive the block containing the wire form buttons and position the block relative to the second printed circuit board. In the preferred embodiment, the hydraulic control valve is included in an electro-hydraulic brake system.
The electrical connector can also be utilized to provide an electrical connection between a printed circuit board and a solenoid coil.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.